CHLOROPHYLL AND THE CHLOROPLASTS 353 



nated, a difference in potential is set up between the electrodes. Dixon 

 and Poole ^^ and Dixon and Ball ^- have shown that the light of the 

 frequency effective in photosynthesis does not produce a photo-electric 

 effect with preparations of chlorophyll. 



Solutions of chlorophyll exert a very decided photodynamic effect. 

 When very dilute methyl alcohol solutions of chlorophyll are injected 

 into the blood stream of animals and these exposed to light, an hemolysis 

 of the red blood corpuscles takes place, in quite the same manner as 

 that brought about by dilute solutions of fluorescent dyes. This action 

 has been studied by Hausmann.^^ 



Chlorophyll, in common with many fluorescent substances, also is 

 capable of sensitizing photographic plates. From this fact the idea was 

 developed that chlorophyll acts as a "sensitizer" in the photosynthetic 

 reaction.^* 



Carotin can be crystallized from carbon bisulfide by the addition of 

 absolute alcohol. Its solubility at 25°, as determined by Schertz,^^ is 

 as follows: in absolute alcohol 15.5 mg. per liter, in petroleum ether 

 (30-50°) 626 mg. per liter, in pure absolute ether 1,005 mg. per liter. 

 In acetone carotin is but slightly soluble, easily in benzol, chloroform 

 and carbon bisulfide. It melts at 174°, but this varies slightly with the 

 rate of heating. In concentrated sulphuric acid carotin dissolves forming 

 an indigo-blue color. Its solutions in alcohol have two absorption bands 

 in the blue and an end absorption in the violet; there is also a faint 

 absorption band in the violet (?i = 425 \i\Ji). The absorption bands of a 

 solution of carotin in carbon bisulfide are displaced toward the red 

 end of the spectrum as compared with alcoholic solutions. The following 

 absorption bands have been determined by Willstatter and Stoll with a 

 grating. The limit of the end absorption in alcohol was determined with 

 a spectrograph in 10 mm. layer as X = 430 [x^. 



TABLE 44 



Absorption Spectrum of 0.005 G. Carotin in 1 Liter of Alcohol and of Carbon 



Bisulfide. (Willstatter and Stoll.) 



Solvent Alcohol Carbon Bisulfide 



Thickness of layer 



in mm. 5 



Band I 492 478 



Band II 459 446 



End absorption . . . 415 — 



Xanthophyll can be crystallized in beautiful plates from saturated alco- 

 holic solutions. Although solutions of carotin and xanthophyll are very 



"Dixon and Poole, Notes from the Botanical School of Trinity College, Dublin, 



3, 90 (1920). 



^^DixonandBall, i^iJ., 3, 199 (1922). . .. ron /1o^^^ 



'^Hausmann. Biochem. Zeit., 12, 331 (1908) ; Jahrb. zmss. Bot., 46, 599 (1909)^ 

 =* Timiriazeff, Covipt. rend., 100, 851 (1885); 102, 686 (1886); 109, 3/9 (1889). 



Liesegang, Chem. Zentr., 1894, I, 636. 



"Schertz, Jour. Agri. Resear., 30, 469 (1925). 



